LK Underfloor Heating using LK Slotted and Turning Boards Wood 22 is intended for installation on standard wood joist floors of a max. 600mm c/c. The construction comprises of a load-bearing slotted 22mm chipboard floor, which replaces the standard board in floor construction. LK Wood 22 is manufactured from environmentally approved and labelled floor grade chipboard (NOTE: as c/c 400mm is standard for the UK, c/c 600mm systems are safe).